A component having a closed-pore metal foam part and a method for its production is known, for example, from U.S. Pat. No. 5,151,246. The component may for example consist of a sleeve, in the interior of which the closed-pore metal foam is accommodated. Blowing agents, for example metal hydrides, in particular titanium hydride, or carbonates, for example calcium carbonate, are used in order to produce this closed-pore metal foam part. From these blowing agents and the metal which is intended to form the metal foam, a composite is produced, which may for example consist of particles of the two substances and which is compacted by pressing. The green body formed in this way can subsequently be subjected to a heat treatment, in which case the temperature must be high enough so that, on the one hand, bonding takes place between the individual powder particles of the metal and, on the other hand, the blowing agent forms a blowing gas. In order to ensure bonding between the metal particles, at least diffusion processes between the particles must be made possible. To this end, sufficient heating of the metal substance must be carried out. With said blowing agents, particles of metals which have a solidus temperature of up to 660° can be foamed.
Metal foams are used, for example, in order to seal housing structures. According to WO 2008/145173 A1, this is for example advantageous in the case of gas discharge lamps which are mounted in a lamp body. In order to permit electrical contacting, contacts must be fed out from the lamp body, in which case hermetic sealing of these feed-throughs must be ensured so that no oxygen enters the interior of the lamp. The feed-through between the lamp body and the metal electrode can be reliably filled by means of a metal foam.
Furthermore, the chosen blowing agent must be selected in terms of its thermal properties in such a way that it is compatible with the solidus temperature of the metal to be foamed (or of the metal alloy to be foamed). In this case, the temperature difference between the solidus temperature of the metal and the lower temperature, at which the blowing agent releases the blowing gas, must not be more than 120° C. Only in this way is it possible to ensure that a metal foam is formed reliably. When metal foams are referred to below, this is also meant to include foams of metal alloys.